We recently completed an NCCAM-funded R21 clinical trial entitled "Variation in the ALOX5 gene and response to omega-3 fatty acid supplements" (R21 AT003411, C. Stephensen, PI;ClinicalTrials.gov Identifier, NCT00536185). A total of 116 subjects of African ancestry were randomized within ALOX5 promoter genotypes to 5 g/day fish oil concentrate or 5 g/day corn/soy placebo oil for a six week intervention;98 subjects completed the trial. In brief, there was a significant, beneficial effect of fish oil supplementation on plasma lipid and lipoprotein profiles and on markers of inflammation. However, there was a wide range of responses for these variables. We hypothesize that accounting for variability in subject responses to fish oil intervention will increase our ability to see significant differences in markers of inflammation linked to development of chronic inflammatory diseases. In the present proposal we plan to use two markers of response to supplementation to quantify this variability. The first marker is the change in fatty acid composition of erythrocyte cell membranes in response to supplementation, focusing on arachadonic acid (AA) and the two principal omega-3 fatty acids from fish oil, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These data are available from the parent study. The second marker set will be developed from plasma concentrations of a panel of 18- to 20-carbon omega-3 and omega-6 fatty acid metabolites that will be measured along with an array of leukotrienes (LT), prostaglandins (PG) and thromboxanes (TX) for the study proposed here. We will determine if these erythrocyte or plasma biomarkers of omega-3 intake will predict changes in markers of inflammation by specific, highly purified cell types (monocyte, granulocyte, lymphocyte) more reliably than using the fish oil/placebo designation. Monocyte data are available from the parent study while granulocyte and lymphocyte samples saved from the parent study will be analyzed for this proposal. We will also determine if these biomarkers will predict changes in plasma markers of systemic inflammation, including plasma concentrations of LT, PG and TX measured for this study, and concentrations of 46 plasma protein markers of inflammation to be measured for this study, including cytokines, chemokines, soluble cell adhesion molecules, acute phase proteins, proteases and anti-proteases, and complement components. PUBLIC HEALTH RELEVANCE: Chronic inflammatory diseases are a major health concern for the US population. Dietary and other complementary and alternative medicine interventions can decrease the severity of such inflammation and thus improve health. Evaluating the impact of such interventions on inflammation is difficult because of the variability of response by individuals resulting from behavioral, environmental and genetic differences. In this study we will develop and evaluate biomarkers of response to intake of fish oil supplements that will improve our ability to evaluate the impact of such interventions on inflammation and risk of chronic inflammatory disease.